Microsoft.BingAds

please could you give me some help

I'm trying to read the campaigns

var authorizationData = new AuthorizationData

            {

                Authentication = new OAuthWebAuthCodeGrant(ClientId, ClientSecret, new Uri(" https://www.erp.kalunga/auth2/callback"), ApiEnvironment.Production),

                DeveloperToken = DeveloperToken,

                CustomerId = CustomerId,

                AccountId = AccountId,

            };

            // Example: Retrieve Campaigns

            var campaignManagementService = new ServiceClient<ICampaignManagementService>(authorizationData);

            var request = new GetCampaignsByAccountIdRequest

            {

                CustomerId = "x",

                UserName = "x",

                Password = "x",

                ApplicationToken = "X",

                CustomerAccountId = "x",

                DeveloperToken = "X"

            };

            return (await campaignManagementService.CallAsync((s, r) => s.GetCampaignsByAccountIdAsync(r), request));

System.InvalidOperationException: 'OAuth access token hasn't been requested. Please request it using the corresponding OAuth class method before calling this method'